The present Assignee's U.S. Pat. No. 4,868,791 describes a method and an apparatus for detecting and correcting an electrode, in particular for use in shock wave generator apparatuses, the method and apparatus making use of a feeler finger that is brought to the focal point, and constituted, in particular, by the rod of an actuator. As can be seen from FIG. 4 of U.S. Pat. No. 4,868,791, a resistance is connected in parallel between the electrodes, said resistance usually being about 10 kilohms. A switch is also provided to ground the positive electrode during a detection test in combination with the feeler finger.
It is necessary for the resistance of about 10 kilohms to be present for the purpose of fixing the potential between the electrodes, for safety reasons. During an electrical discharge, it will be understood that as much current as possible must pass between the electrodes in order to obtain maximum effectiveness of the shock wave, thereby implying that the resistance must be relatively high in order to prevent it absorbing too much current.
Unfortunately, this conflicts with correcting the centering of the electrodes where it is desirable to detect changes in resistance that are much less than about 10 kilohms when the electrode is very close to the feeler finger. In that prior patent of the Assignee, the grounding switch used is an expensive component is that bulky and difficult to implement since it is a switch that must be capable of isolating voltages lying in the range 10 kV to 20 kV, while also being capable of being driven by an external source, e.g. compressed air. In addition, like any mechanical member, it suffers from problems of reliability over a period of time and requires maintenance.
An object of the present invention is thus to solve the novel technical problem consisting in providing an electrical discharge circuit for providing a discharge between two discharge electrodes that are immersed in a liquid, the circuit being capable of fixing the low frequency potential of the positive electrode.
Another object of the present invention is to solve the novel technical problem consisting in providing an electrical discharge circuit for providing a discharge between two discharge electrodes, immersed in a liquid, the circuit making it possible to detect and correct electrode positions in a manner that is simpler, more reliable, and less expensive, thus being suitable for use on an industrial scale.
Another object of the present invention is to solve the novel technical problem consisting in providing a discharge circuit suitable for use in apparatuses for generating pressure waves, as used in therapeutic treatments such as lithotrity, osteotrity (bone treatment), or treatment of tissue, in particular tumors, with the discharge electrodes being immersed in a liquid.
These technical problems are solved for the first time by the present invention in a manner that is satisfactory, reliable, cheap, and usable on an industrial scale.